Hundreds of protesters were locked in a standoff with police in northern Peru on Wednesday as they vowed to stop Newmont Mining from transferring water from a lake to a reservoir as part of its $5 billion Conga gold project.

Residents and local officials said it was the second straight day of tensions near the proposed mine that would be Peru's most expensive ever.

On Tuesday, a minor clash between protesters and police marked an end to a stretch of relative calm since August, when the government of President Ollanta Humala said it would stop trying to overcome local opposition to the mine.

The new round of protests came after a top official for the Conga project - Chief Executive Roque Benavides of Newmont's partner Buenaventura - told Reuters last week that water from Perol would be transferred to a new reservoir later this year.

He said that construction of the mine would begin if the company could pump water from Lake Perol into the second of four reservoirs it is building without sparking broad local opposition.

Lake Perol is one of several alpine lakes in Cajamarca that would be affected by the proposed mine, which would essentially extend the life of the nearby Yanacocha mine the two companies run.

Humala has twice shuffled his cabinet since taking office in 2011 in large part because of violent protests over Conga.

Yanacocha officials said many locals support the construction of the reservoir because it will provide water year round instead of seasonally.

"The reservoir has been received very well by the population because they want to see its benefits," said Javier Velarde, Yanacocha's general manager of corporate affairs, said on local TV.

Another representative of Newmont and Buenaventura declined comment.

Despite an extensive environmental study and revisions to the project's original plan, communities in Cajamarca still say they fear the Conga project will pollute and deplete nearby lakes and rivers.

"The mine needs water for its project and it's going to give us polluted water," said Wilfredo Saavedra, who leads a community group. "We want them to leave us alone with our lakes, which are enough for us."

Milton Sanchez, another community leader, said a group of protesters who call themselves "the guardians of the lake" were making their way by foot and horse to "inspect" Lake Perol on Tuesday when they were attacked by police officers.

Police said they fired a single rubber bullet after being pelted with rocks.

Five people were killed in clashes with police last year, and Humala faced criticism because police live rounds at protests.